class_docstr: Pan-zoom transform
  
  Parameters
  ----------
  canvas : instance of Canvas | None
      The canvas to attch to.
  aspect : float | None
      The aspect ratio to apply.
  **kwargs : dict
      Keyword arguments to pass to the underlying `STTransform`.
code: def canvas_tr(self):
      return STTransform.from_mapping(
          [(0, 0), self._canvas.size], [(-1, 1), (1, -1)]
      )
  
file_path: vispy/vispy/visuals/transforms/interactive.py
imports: from __future__ import division
  import numpy
  from .linear import STTransform
label_desc: Use image node_id 3 for calling the PanZoomTransform obj's underlying member method code with example usage: obj.canvas_tr() and returns: STTransform